Method for producing semiconductor device having alignment mark

ABSTRACT

An alignment method for a semiconductor device having a conductive thin film on a conductive substrate surface across an insulation film, comprises steps of: forming in the insulation film, at least two apertures exposing the substrate surface therein; selectively depositing a conductive material in the apertures thereby forming a stepped portion in at least one of said apertures; and forming the conductive thin film at least on said insulation film. The alignment is conducted utilizing the stepped portion.

This application is a continuation of application Ser. No. 08/183,254filed Jan. 19, 1994, now U.S. Pat. No. 5,482,893 which is a continuationof application No. 07/722,107 filed Jun. 27, 1991, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for producing a semiconductordevice such as a memory, a photoelectric converting device, a signalprocessing device or the like adapted for use in various electronicappliances, and more particularly to a method for producing asemiconductor device featuring an alignment mark structure.

2. Related Background Art

In the formation of wiring layers by patterning in conventionalsemiconductor devices, the precision of the patterning is improved byautomatic alignment utilizing a recess, formed in a predeterminedposition in advance, as a mark. For example, in a conventionalsemiconductor device including a CMOS transistor as shown in FIG. 1,oxide films 2, 4 on the principal surface of a substrate 1 are partiallyremoved at a predetermined position by selective etching to expose thesilicon surface, thus forming a mother mark 6. Then, the entiresubstrate surface, including the mother mark 6, is covered by a metalfilm 9, thereby forming a recess 10 on the metal film, corresponding tothe form of the mother mark 6. A wiring layer of a desired pattern isobtained by patterning the metal film, utilizing auto-alignment achievedby irradiating the recess with a laser beam and detecting the reflectedlight, or by utilizing data obtained by image processing such as TV-AA(television auto-alignment).

However, in such a conventional semiconductor device, if the metal filmis formed by a selective metal depositing method such as tungstenchemical vapor deposition method (CVD) to a thickness required for thewiring layer, the mother mark area and the metal film therearound becomeflat so that the recess corresponding to the mother mark is no longerformed, because of the selective growth characteristic of the depositingmethod. Consequently the detection of the mother mark, essential forauto alignment, becomes difficult and the precision of alignmentsignificantly deteriorates.

FIG. 2 shows the wiring layer formed by selected deposition utilizingthe tungsten CVD mentioned above.

On the mother mark 6, a metal film composed of tungsten is deposited tothe level of the insulation film 4, so that the portion 10, which is toserve as an alignment mark in a next step, has become flat.

SUMMARY OF THE INVENTION

In consideration of the technical drawbacks of the prior technologymentioned above, an object of the present invention is to provide asemiconductor device allowing easy confirmation of the position of amother mark for mask alignment and enabling a high-density wiringstructure, a producing method therefor and an alignment method therefor.

Another object of the present invention is to provide a method forproducing a semiconductor device having a conductive thin film on aconductive substrate across an insulation film, comprising steps offorming at least two apertures in the insulation film to expose thesubstrate therein, selectively depositing a conductive material in theapertures thereby forming a stepped portion at least in one of theapertures, and forming the conductive film at least on the insulationfilm, wherein the stepped portion is utilized for alignment.

As the present invention is capable, utilizing selective metaldeposition by a novel chemical vapor deposition (CVD) method, of forminga portion faithfully corresponding to the form of a stepped portionconstituting an alignment mark on a conductive film, a faithfulphotoresist pattern can be formed on the substrate surface byauto-alignment in the patterning of a wiring layer.

Still another object of the present invention is to provide a method forproducing a semiconductor device having a conductive thin film on aconductive substrate across an insulation film, comprising steps offorming an aperture in the insulation film to expose the substratesurface, forming a stepped portion not exposing the substrate surface inthe insulation film, selectively depositing a conductive material in theaperture, and forming the conductive film at least on the insulationfilm, wherein the stepped portion is utilized for alignment.

The present invention is capable, utilizing selective metal depositionby a novel CVD method, of selectively depositing a conductive materialsolely in the aperture exposing the conductive substrate surface,thereby forming a conductor. By forming a conductive layer bynon-selective deposition, on the above-mentioned conductor and on astepped portion formed in the insulation film on the substrate surface,a portion corresponding to the form of the stepped portion can be formedin the thus obtained conductive layer. The portion can be utilized as analignment mark to achieve formation of a faithful wiring pattern byauto-alignment in the patterning of the conductive layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are schematic views showing conventional methods forforming an alignment mark;

FIG. 3 is a schematic view showing a method for forming an alignmentmark according to a first embodiment of the present invention;

FIGS. 4A to 4D are schematic views showing a method for producing asemiconductor device according to the first embodiment;

FIG. 5 is a schematic view showing a method for forming an alignmentmark according to a second embodiment of the present invention;

FIG. 6 is a schematic view showing a method for forming an alignmentmark according to a third embodiment of the present invention;

FIGS. 7A to 7C are schematic views showing a method for producing asemiconductor device according to the third embodiment;

FIG. 8 is a schematic view showing a method for forming an alignmentmark according to a fourth embodiment of the present invention;

FIGS. 9A to 9E are schematic views showing a method for producing asemiconductor device according to the fourth embodiment;

FIG. 10 is a schematic view showing a method for forming an alignmentmark according to a fifth embodiment of the present invention;

FIGS. 11A to 11C are schematic views showing a method for producing asemiconductor device according to the fifth embodiment;

FIGS. 12 to 15 are views showing an example of the manufacturingapparatus adapted for use in the method of the present invention; and

FIGS. 16A to 16D are schematic perspective views showing the steps ofwiring layer formation according to the method of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention includes a method for producing a semiconductordevice and an alignment method therefor.

For example, the present invention includes an alignment method for asemiconductor device having a conductive thin film on a conductivesubstrate surface across an insulation film, comprising steps of:

forming at least two apertures exposing the substrate surface therein inthe insulation film;

selectively depositing a conductive material in the apertures to burythe apertures, thereby forming a stepped portion at least in one of theapertures; and

forming the conductive thin film at least on the insulation film;

wherein alignment in patterning the conductive thin film is conductedutilizing the stepped portion.

Also the present invention includes a method for producing asemiconductor device having a wiring layer on a conductive substratesurface across an insulation film, comprising steps of:

forming at least two apertures in the insulation film, exposing thesubstrate surface;

selectively depositing a conductive material in the apertures therebyforming a stepped portion serving an alignment mark in at least one ofthe apertures;

forming a conductive thin film for forming the wiring layer at least onthe insulation film; and

forming the wiring layer by patterning the conductive thin film by maskalignment with the stepped portion as the alignment mark.

Furthermore the present invention includes an alignment method for asemiconductor device having a conductive thin film on a conductivesubstrate surface across an insulation film, comprising steps of:

forming an aperture exposing the substrate surface in the insulationfilm;

forming a stepped portion not exposing the substrate surface in theinsulation film;

selectively depositing a conductive material in the aperture; and

forming the conductive thin film at least on the insulation film;

wherein alignment is conducted utilizing the stepped portion.

Furthermore the present invention includes a method for producing asemiconductor device having a wiring layer on a conductive substratesurface across an insulation film, comprising steps of:

forming an aperture exposing the substrate surface in the insulationfilm;

forming a stepping portion not exposing the substrate surface in theinsulation film;

selectively depositing a conductive material in the aperture;

forming a conductive thin film for forming the wiring layer at least onthe insulation film; and

forming the wiring layer by patterning the conductive thin film, by maskalignment utilizing the stepped portion as an alignment mark.

In the execution of the present invention, the shape of the steppedportion serving as an alignment mark and the planar form thereof are notparticularly limited but are only required to be large enough forproviding a mark detection signal for alignment. The step is preferably400 Å or larger, and most preferably 500 Å or larger.

Also the method for depositing metal in contact holes for wiring ispreferably a selective deposition of a metal film principally composedof aluminum, utilizing alkylaluminum hydride gas and hydrogen.

[Embodiment 1]

Now the present invention will be clarified in detail by an embodimentshown in the attached drawings.

FIG. 3 illustrates a semiconductor device constituting a preferredembodiment of the present invention. A semiconductor substrate 1 iscomposed for example of silicon, and is provided thereon with functionalelements such as MOS transistors, bipolar transistors or the like. 0nthe principal surface of the substrate 1 there are formed, insuccession, a thermal oxide film 2 and an interlayer insulation film 4,in which opened are a contact hole 5 and a mother alignment mark 6constituting a stepped portion. In the present embodiment, the contacthole 5 and the mother mark 6 have the same planar area. A diffusionlayer 3 is formed from the bottom of the contact hole 5 to the interiorof the semiconductor substrate 1.

In the contact hole 5 and mother mark 6, there is selectively depositeda conductive material such as aluminum by a special CVD method to beexplained layer, thereby forming a wiring layer 7 and a metal film 8,formed as conductors positioned lower than the upper surface of theinterlayer insulation film 4. Also a wiring layer 9 composed of anon-selectively deposited conductive layer, is formed on the wiringlayer 7 and metal film 8, and on the interlayer insulation film 4.

In the semiconductor device of such a structure, a recess 10 is formedin the wiring layer 9 above the mother mark 6, as a stepped portioncorresponding to the form of the step in the mother mark 6, and is usedas an alignment mark for auto-alignment in the patterning of the wiringlayer 9. In the semiconductor device, since the recess 10 can be formedprecisely at the position of the mother mark 6 mentioned above, thewirings can be obtained precisely according to the design, by apatterning operation utilizing the recess 10 as the alignment mark.Since the patterning is not positionally aberrated, high-density wiringsare also possible.

The metal to be employed for electrode leads and wirings can be Al, analloy principally composed of aluminum such as Al--Si, Al--Cu,Al--Si--Ti or Al--Si--Cu; Cu, Mo or W or alloys thereof. For filling thecontact hole for electrode extraction, there is preferably employed theAl-CVD method to be explained later. The insulation film is preferablycomposed of an inorganic material such as silicon oxide or siliconnitride formed by CVD or sputtering, PSG (phosphosilicate glass) or PBSG(borophosphosilicate glass), or an organic material such as polyamide.The wiring layer on the insulation film can be formed for example byforming a metal layer by CVD or sputtering on the entire insulation filmfollowed by patterning of the metal layer into the form of desiredwirings by a photolithographic process, or by modifying the desiredparts of the insulation film and depositing a metal selectively on thusmodified surfacial parts.

The stepped portion 10 for alignment has a step preferably of 400 Å orlarger, and more preferably of 500 Å or larger.

In the following there will be explained the method for producing thesemiconductor device shown in FIG. 3, with reference to FIGS. 4A to 4D

At first, on a silicon semiconductor substrate 1, constituting aconductive substrate and bearing functional elements such as MOStransistors or bipolar transistors, a thermal silicon oxide film 2 isformed by CVD (FIG. 4A). Then, with patterned photoresist, ionimplantation is conducted in a predetermined area of the thermal oxidefilm 2, and a thermal treatment is applied to form a diffusion layer 3(FIG. 4B). Subsequently an interlayer insulation film 4 of siliconnitride is deposited by CVD on the thermal oxide film 2, then heattreated, and subjected to contact patterning. Subsequently a contacthole 5 for electrode extraction and a stepped mother mark 6 of the sameplanar area as that of the contact hole 5 are formed by etching to thesurface of the semiconductor substrate 1 (FIG. 4C). Then Al--Si isselectively deposited in the contact hole 5 and mother mark 6 to form afirst conductive wiring layer 7 in the contact hole 5 and a conductivemetal film 8 in the mother mark 6. In the present embodiment, theformation of the metal film 8 is terminated at a level lower than theupper surface of the interlayer insulation film 4, whereby the metalfilm 8 constitutes a stepped recess to the surrounding interlayerinsulation film 4. Also in this embodiment, since the contact hole 5 andthe mother mark 6 have the same planar area, the first wiring layer 7and the metal film 8 are present at the same height from the surface ofthe substrate 1 (FIG. 4D).

Subsequently, the entire surface of the semiconductor substrate 1 shownin FIG. 4D is modified by RF plasma treatment, and Al--Si isnon-selectively deposited over the entire surface by CVD to form asecond wiring layer 9. Thus, the recessed form of the mother mark 6 isreflected in the upper surface of the second wiring layer 9 to form astepped recess 10 (cf. FIG. 3). The patterning operation of the wiringlayer with automatic mask alignment, by irradiating the recess 10 with alaser beam and detecting the reflected light, allows the forming ofdesired wiring patterns exactly on the semiconductor substrate 1 andimproves the production yield of the semiconductor device.

In the above-explained embodiment, prior to the formation of the secondwiring layer 9 on the interlayer insulation film 4, the surface thereofmay be planarized by a SOG (spin-on glass) method. More specifically, asolution of silanol compound in organic solvent (alcohol or ketone) isspin coated with a spin coater for 15-30 seconds at a revolution of3,000-6,000 rpm, with a back rinse with isopropyl alcohol, and thesemiconductor substrate is baked on a hot plate for 1-3 minutes at80°-200° C. The surface irregularities of the interlayer insulation filmare almost eliminated by such process, so that the second wiring layerbecomes free from an increase in resistance or breakage at steps,resulting from such surface irregularities.

[Embodiment 2]

FIG. 5 is a schematic cross-sectional view showing another preferredembodiment of the present invention, in which, in contrast to thestructure shown in FIG. 3, a metal film 11 on the stepped mother mark 6and a wiring layer 12 for electrode extraction are deposited higher thanthe upper surface of the interlayer insulation film 4. In thisembodiment, therefore, a projection 13 is formed on the upper surface ofa metal film 9 above the mother mark 6, corresponding to the form of themother mark 6. The projection 13 can be used as an alignment mark forautomatic mask alignment in the patterning of the wiring layer, in asimilar manner as the recess 10 explained before.

[Embodiment 3]

FIG. 6 is a schematic cross-sectional view showing another preferredembodiment of the present invention. In this embodiment, different fromthose shown in FIGS. 3 and 5, the planar area of the stepped mother mark14 is made sufficiently larger than that of the contact hole 5, in orderto utilize the size dependence of the film growth rate in the selectivemetal deposition in the CVD method to be explained later. Morespecifically, in selective metal deposition into holes of differentsizes, the film growth rate in a smaller hole is higher than that in alarger hole. Consequently the film growth rate in this case is lower inthe mother mark 14 than in the contact hole 5.

The producing method for the semiconductor device shown tn FIG. 6 willbe explained with reference to FIGS. 7A to 7C.

At first a thermal oxide film 2 is formed on the principal surface ofthe semiconductor substrate 1, and ion implantation with patternedphotoresist and thermal treatment are conducted to form a diffusionlayer 3 (FIG. 7A). This step is the same as that shown in FIG. 4A. Thenan interlayer insulation film 4 is deposited on the thermal oxide film 2and thermally treated, and a contact hole 5 and a stepped mother mark 14are formed by contact patterning and etching in such a manner that themother mark 14 is larger in planar area than the contact hole (FIG. 7B).

Subsequently Al--Si is deposited by selective deposition in the contacthole 5 and the mother mark 14. The deposition is terminated when theupper surface of the conductive wiring layer 15 in the contact hole 5reaches the level of the upper surface of the interlayer insulation film4. At this point, because of the above-mentioned size dependence of theselective deposition, the metal film 16 deposited in the mother mark 14does not reach the upper surface of the interlayer insulation film 4, sothat the metal film 16 constitutes a recess to the surroundinginsulation film 4 (FIG. 7C).

Thus, at the contact for the electrode, the upper surface of the wiringlayer 15 can be planarized with that of the interlayer insulation film4, while the recessed form of the mother mark 14 can still be utilizedas the alignment mark for mask alignment in the patterning of the wiringlayer.

Subsequently the entire surface of the semiconductor substrate 1 shownin FIG. 7C is modified by RF plasma treatment, and is subjected tonon-selective deposition of Al--Si by CVD, thereby forming a secondwiring layer 9, whereby the recessed form of the mother mark 14 isreflected as a stepped recess 17 in the upper surface of the wiringlayer 9 (FIG. 6). In such a semiconductor device, desired wiringpatterns could be exactly formed on the semiconductor substrate 1 by apatterning operation of the wiring layer utilizing automask alignmentbased on irradiation of the recess 17 with a laser beam and detection ofthe reflected light, in a similar manner as the recess 10 shown in FIG.3.

As explained in the foregoing, the present invention is capable, basedon selective metal deposition by a novel CVD method, of forming aportion faithfully corresponding to the shape of a stepped portion onthe upper face of a conductive thin film as a mask alignment mark,whereby a photoresist pattern can be faithfully formed on the substratesurface by auto-alignment in the patterning of a wiring layer.

[Embodiment 4]

FIG. 8 shows a preferred embodiment of the present invention, wherein asemiconductor substrate 1 is composed, for example, of silicon andconstitutes a conductive substrate on which are formed functionalelements, such as MOS or bipolar transistors. In predetermined areas onthe principal plane of the substrate 1, there are formed a field oxidefilm 22 of a larger thickness and a gate oxide film 2 of a smallerthickness. A diffusion layer 3 is provided in the semiconductorsubstrate 1 under a predetermined area of said gate oxide film 2. Aninterlayer insulation film 4 is formed with a predetermined thickness onthe field oxide film 22 and the gate oxide film 2. Above the diffusionlayer 3, a contact hole 8 is formed by opening the gate oxide film 2 andthe interlayer insulation film 4 by etching so as to expose the uppersurface of the diffusion layer 3. Also in a predetermined area of theinterlayer insulation film 4 and the field oxide film 22 thereunder, astepped mother mark 9 is formed by etching from the upper surface of theinterlayer insulation film 4 to the interior of the field oxide film 22.

In the above-mentioned contact hole 8, a first wiring layer 7 as aconductor for electrode extraction is formed by selective deposition forexample of aluminum by a special CVD method to be explained later, tothe upper surface of the interlayer insulation film 4. Also a secondwiring layer 11, composed of a conductive layer, is formed bynon-selective deposition of a conductive material on the first wiringlayer 7, on the interlayer insulation film 4 and inside the mother mark9.

In the semiconductor device of such a structure, a recess 10 is formedin the second wiring layer 11 above the mother mark 9, as a steppedportion corresponding to the form of the step in the mother mark 9, andis used as an alignment mark for auto-alignment in the patterning of thesecond wiring layer 11. In the semiconductor device, since the recess 10can be formed precisely at the position of the mother mark 9 mentionedabove, the wirings can be obtained precisely according to the design, bya patterning operation utilizing the recess 10 as the alignment mark.Since the patterning is not positionally aberrated, high-density wiringsare also possible.

The metal to be employed for electrode leads and wirings can be Al, oran alloy principally composed of aluminum such as Al--Si, Al--Cu,Al--Si--Ti or Al--Si--Cu; Cu, Mo or W or an alloy thereof. For fillingthe contact hole, for electrode extraction, there is preferably employedthe Al-CVD method to be explained later. The insulation film ispreferably composed of an inorganic material such as silicon oxide orsilicon nitride formed by CVD or sputtering, PSG (phosphosilicate glass)or PBSC (borophosphosilicate glass), or an organic material such aspolyimide. The wiring layer on the insulation film can be formed forexample by forming a metal layer by CVD or sputtering on the entireinsulation film followed by patterning of the metal layer into the formof desired wirings by a photolithographic process, or by modifying thedesired parts of the insulation film and depositing a metal selectivelyon thus modified surfacial parts.

The step for the alignment mark is preferably 400 Å or larger, and morepreferably 500 Å or larger.

In the following there will be explained the method for producing thesemiconductor device shown in FIG. 8, with reference to FIGS. 9A to 9E.

At first, on a silicon semiconductor substrate 1, constituting aconductive substrate and bearing function elements such as MOS orbipolar transistors thereon, a thermal silicon oxide film 1' was formedby CVD, and, in a predetermined area of the film 1', there was formed afilm 1" of high oxidation resistance, such as a silicon nitride film, byCVD (FIG. 9A).

Then selective oxidation was applied to the thermal oxide film 1' andthe anti-oxidation film 1" to form a field oxide film 22. Thenanti-oxidation film 1" and the thermal oxide film 1' thereunder wereremoved, and oxidation was again conducted to form a layer 2constituting the gate oxide film. A polysilicon film (not shown) wasdeposited in a predetermined area of the gate oxide film 2, and ionimplantation through a photoresist pattern, followed by thermaltreatment, was conducted to form a diffusion layer 3 (FIG. 9B).Subsequently an interlayer insulation film 4 was formed by CVD over theentire surface of the semiconductor substrate 1 (FIG. 9C). Theinterlayer insulation film 4 was provided for electrical separation ofthe above-mentioned polysilicon film from an Al-CVD film to be explainedlater.

Then, the interlayer insulation film 4 was subjected to a patterningprocess to form a contact hole 8 for electrode extraction, exposing thediffusion layer 3 therein and a mother mark 9 as a step reaching theinterior of the field oxide film 22 (FIG. 9D).

Subsequently Al--Si was selectively deposited in the contact hole 8 bythe aforementioned selective deposing method to form a conductive firstwiring layer 7 until the upper face thereof reaches the upper surface ofthe interlayer insulation film 4 (FIG. 9E).

Then the entire surface of the semiconductor substrate 1, namely thesurface of the first wiring layer 7 and of the interlayer insulationfilm 4 and the interior of the mother mark 9, was subjected to RF plasmatreatment and then to non-selective Al--Si deposition for example bysputtering, and the Al--Si layer was patterned to form a second wiringlayer 11 (cf. FIG. 8). As a result, the recessed form of the steppedmother mark 9 was transferred as a recess 10 on the upper surface of thesecond wiring layer 11. A desired wiring pattern could be exactly formedon the semiconductor Substrate 1 by patterning the second wiring layer11 with automatic mask alignment utilizing irradiation of the recess 10with a laser beam and detection of the reflected light.

In the above-explained embodiment, prior to the formation of the secondwiring layer 11 on the interlayer insulation film 4,.the surface thereofmay be planarized by a SOG (spin-on-glass) method. More specifically asolution of silanol compound in organic solvent (alcohol or ketone) isspin coated with a spin coater for 15-30 seconds at a revolution of3,000-6,000 rpm, with a back rinse with isopropyl alcohol, and thesemiconductor substrate is baked on a hot plate for 1-3 minutes at80°-200° C. The surface irregularities of the interlayer insulation filmare almost eliminated by such a process, so that the second wiring layerbecomes free from an increase in resistance or breakage at steps,resulting from such surface irregularities.

[Embodiment 5]

FIG. 10 is a schematic cross-sectional view showing another preferredembodiment of the present invention. On the principal surface of asemiconductor substrate 12 composed for example of silicon and bearingfunctional elements such as bipolar transistors thereon, there is formedan oxide film 13, and a diffusion layer 14 is formed in the substrate 12under a predetermined area of the oxide film 13. Above the diffusionlayer 14 there is formed a contact hole 15 for example by etching theoxide film 13 so as to expose the upper surface of the diffusion layer14. The contact hole 15 is composed of a lower part 15a having a smallerplanar area and having the bottom on the upper face of the diffusionlayer 14, and an upper part 15b of a larger planar area having thebottom at the upper end of the lower part 15a. Also in a predeterminedarea of the oxide film 13, a mother mark 16 is formed as a step obtainedby etching said oxide film 13 from the upper surface to the interiorthereof.

In the lower part 15a of the contact hole 15, there is formed a firstwiring layer 17 for electrode extraction, obtained by selectivedeposition of a conductive material such as aluminum by theaforementioned selective depositing method to the upper end of the lowerpart 15a. Also a second wiring layer 18, obtained by non-selectivedeposition of a conductive material, is formed on the first wiring layer17 and on the oxide film 13, and in the mother mark 16. The secondwiring layer 18 is provided thereon with a recess 19 above the contacthole 15 and another recess 20 above the mother mark 16. Thus the recess20, formed as a step corresponding tn shape to the mother mark 16, canbe used as an alignment mark for automatic mask alignment in thepatterning of the wiring layer.

Now reference is made to FIGS. 11A to 11C for explaining the producingmethod of the semiconductor device shown in FIG. 10.

A thermal oxide film 13 is formed on the principal surface of asemiconductor substrate 12. Then a photoresist pattern is applied to apredetermined area of the oxide film 13, and ion implantation followedby thermal treatment is conducted to form a diffusion layer 14. Then afirst contact patterning is applied to the oxide film 13 to form ashallow aperture 15c in a predetermined area of the oxide film 13 abovethe diffusion layer 14, and simultaneously a recess 16 of the same depthin a predetermined area of the oxide film 13 (FIG. 11A).

Then, a second patterning is applied to the oxide film 13 to etch thebottom of the aperture 15c so as to expose the diffusion layer 14,thereby forming the lower part 15a of the contact hole 15. At the sametime the periphery of the aperture 15c is etched to form the upper part15b of the contact hole 15 (FIG. 11B).

Subsequently Al--Si is selectively deposited in the lower part 15a ofthe contact hole 15 by the aforementioned selective depositing method toform a conductive first wiring layer 17 to the level of the bottom ofthe upper part 15b (FIG. 11C).

Then, the entire surface of the semiconductor substrate 12, namely thesurface of the oxide film 13 and of the first wiring layer 17 in thecontact hole 15 and the interior of the mother mark 16, are subjected toRF plasma treatment, and then to non-selective deposition of Al--Si forexample by sputtering, followed by patterning to obtain a conductivesecond wiring layer 18 (FIG. 10). As a result, a stepped recess 20 isformed on the second wiring layer 16, corresponding to the form of thestepped mother mark 16.

Thus, a desired wiring pattern could be exactly formed of thesemiconductor substrate 12 in the patterning of the second wiring layer16, by automatic mask alignment utilizing irradiation of the recess 20with a laser beam and detection of the reflected light.

In the embodiments 4 and 5 explained above, the selective metaldeposition by a novel CVD method allows the formation of a conductor bydepositing a conductive material selectively in an aperture in which theconductive substrate is exposed. Thus, by non-selective deposition of aconductive material on the conductor and on a step formed in aninsulation film provided on the substrate surface, there can be formed aportion, in the thus obtained conductor layer, corresponding in shape tothe step. The portion can be utilized as a mask alignment mark in thepatterning of the conductor layer, thereby allowing the obtaining of afaithful wiring pattern of desired shape, for example, byauto-alignment.

In the following there will be explained a film forming method adaptedfor use in the foregoing embodiments 1 to 5, for forming the wiringlayer.

The film forming method is suitable for filling an aperture with aconductive material for the purpose of forming an electrode of theabove-explained structure, and its depositing speed is dependent on thearea of substrate in the aperture.

More specifically, the film forming method suitable for use tn thepresent invention is to form a deposition film on an electron-donatingsubstrate by a surface reaction, utilizing alkylaluminum hydride gas andhydrogen gas (said method being hereinafter called Al-CVD method).

An aluminum film of particularly satisfactory quality can be obtained byemploying monomethylaluminum hydride (MMAH) or dimethylaluminum hydride(DMAH) as the raw material gas and hydrogen gas as the reaction gas, andheating the substrate surface in the presence of a mixture of thesegasses. In the selective aluminum deposition, the substrate surface ispreferably maintained, by direct or indirect heating, at a temperatureat least equal to the decomposition temperature of alkylaluminum hydridebut not exceeding 450° C., more preferably from 260° to 440° C.

The substrate can be heated to the above-mentioned temperature range bydirect or indirect heating, but aluminum film of satisfactory qualitycan be obtained by maintaining the substrate in the temperature range bydirect heating. For example, when the substrate surface temperature ismaintained in the more preferred range of 260°-440° C., a satisfactoryaluminum film can be obtained with a deposition speed of 3000-5000Å/min., which is higher than that obtainable with resistance heating.Such direct heating, in which the substrate itself is heated by directenergy transfer from heating means, can be achieved by heating with alamp, such as a halogen lamp or a xenon lamp. Also indirect heating canbe achieved by resistance heating, for example by a heating resistorprovided in a support member for supporting the substrate in a filmforming chamber.

The above-mentioned method, when applied to a substrate having both anelectron-donating surface area and an electron non-donating surfacearea, forms an aluminum single crystal with satisfactory selectivity,solely on the electron-donating surface area. The aluminum is excellentin all the properties required for an electrode/wiring material,including a reduced frequency of hillocks and a reduced frequency offormation of alloy spikes.

This is presumably because of the fact that aluminum of satisfactoryquality can be selectively formed on a conductive or semiconductivesurface constituting an electron-donating surface and that the aluminum,excellent in crystalline character, scarcely shows formation of alloyspikes resulting from eutectic reactions with the underlying material,such as silicon. The aluminum, when employed as an electrode in thesemiconductor device, shows advantages not anticipated in the priortechnology and beyond the concept of the conventional aluminumelectrode.

As explained in the foregoing, this method provides a monocrystallinestructure in the aluminum deposited in an aperture formed for example inan insulation film and exposing therein an electron-donating surfacesuch as a semiconductive substrate surface, but this Al-CVD method canalso deposit selectively metal films principally composed of aluminumwith satisfactory film quality, as will be explained in the following.

For example a conductive material such as Al--Si, Al--Ti, Al--Cu,Al--Si--Ti or Al--Si--Cu can be deposited by introducing, in addition toalkylaluminum hydride gas and hydrogen:

Si-containing gas such as SiH₄, Si₂ H₆, Si₃ H₈, Si(CH₃)₄, SiCl₄, SiH₂Cl₃ or SiHCl₃ ;

Ti-Containing gas such as TiCl₄, TiBr₄ or Ti(CH₃)₄ ; and

Cu-containing gas such as copper bisacetylacetonate (Cu(C₅ H₇ O₂)),copper bisdipivaloylmethanite (Cu(C₁₁ H₁₉ O₂)₂) or copperbishexafluoroacetylacetonate (Cu(C₅ HF₆ O₂)₂); in suitable combination,as a gaseous mixture.

Also since the Al-CVD method is capable of selective film formation andproviding satisfactory surface characteristics in the deposited film,there may be employed a non-selective film forming method in a next stepto form an aluminum film or a metal film principally composed ofaluminum, on the selectively deposited aluminum film and on aninsulation film composed, for example, of SiO₂, thereby obtaining ametal film widely usable for wirings of the semiconductor device.

Examples of such a metal film include combinations of selectivelydeposited Al, Al--Si, Al--Ti, Al--Cu, Al--Si--Ti or Al--Si--Cu andnon-selectively deposited Al, Al--Si, Al--Ti, Al--Cu, Al--Si--Ti orAl--Si--Cu.

The non-selective film deposition can be achieved, for example, by a CVDmethod other than the Al-CVD method or by sputtering.

[Film forming apparatus]

In the following there will be described a film forming apparatusadapted for use in electrode formation according to the presentinvention.

FIGS. 12 to 14 illustrate a continuous metal film forming apparatusadapted for use in the film forming method explained above.

The continuous film forming apparatus consists, as shown in FIG. 12, ofa loading chamber 311, a CVD reaction chamber 312 serving as a firstfilm forming chamber, an Rf etching chamber 313, a sputtering chamber314 serving as a second film forming chamber, and an unloading chamber315, which can mutually communicate by gate valves 310a-310f in a sealedstate from the external atmosphere and can be independently evacuated byvacuum systems 316a-316e. The loading chamber 311 is provided to replacethe atmosphere of the substrate prior to deposition with hydrogen gas,in order to increase the throughput. The next CVD reaction chamber 312conducts the selective deposition by the aforementioned Al-CVD methodonto the substrate under an ordinary or low pressure, is providedtherein with a substrate holder 318 equipped with a heating resistor 317for heating the substrate surface to be subjected to the film depositionat least within a temperature range of 200°-450° C., and is furtherprovided with a raw material gas line 319 for introducing raw materialgas such as alkylaluminum hydride gasified by bubbling with hydrogen gasin a bubbler 319-1 and another gas line 319' for introducing hydrogengas as the reaction gas. The Rf etching chamber 313, for cleaning(etching) the substrate surface after selective deposition in argonatmosphere, is provided therein with a substrate holder 320 capable ofheating the substrate at least within a temperature range of 100°-250°C. and an RF etching electrode line 321, and is further provided with anargon gas supply line 322. The sputtering chamber 314, for non-selectivedeposition of a metal film by sputtering onto the substrate surface inan argon atmosphere, is equipped therein with a substrate holder 323 forheating the substrate at least within a range of 200°-250° C. and atarget electrode 324 for supporting a sputtering target 324a, and isalso provided with an argon gas supply line 325. The final unloadingchamber 315, for adjustment of the substrate after metal film depositionbefore the transfer of the substrate to the exterior, is capable ofreplacing the atmosphere with nitrogen.

FIG. 13 shows another structure of the continuous metal film formingapparatus suitable for use in the above-explained film forming method,wherein the same components as those in FIG. 12 are represented by samenumbers. The apparatus in FIG. 13 is different from that in FIG. 12 inthat the substrate surface can be directly heated by halogen lamps 330constituting direct heating means, and in that the substrate holder 312is provided with projections 331 for supporting the substrate in afloating state for such direct heating.

The direct heating of the substrate surface with such structure allowsthe obtaining of an increased deposition speed, as explained already inthe foregoing.

The continuous metal film forming apparatus of the above-explainedstructure is in practice equivalent to a structure shown in FIG. 14, inwhich the loading chamber 311, CVD reaction chamber 312, Rf etchingchamber 313, sputtering chamber 314 and unloading chamber 315 aremutually linked through a transfer chamber 326, wherein the loadingchamber 311 also serves as the unloading chamber 315. The transferchamber 326 is provided, as shown in FIG. 14, with an arm 327 which canrotate in both directions AA and telescope in directions BB and cantransfer the substrate in succession from the loading chamber 311through the CVD reaction chamber 312, Rf etching chamber 313, and thesputtering chamber 314 to the unloading chamber 315 without exposure tothe external atmosphere.

[Film forming procedure]

In the following there will be described the film forming procedure forforming electrodes and wirings according to the present invention.

FIGS. 16A to 16D are schematic perspective views showing the steps ofthe film forming procedure.

At first described is the outline of the procedure. A semiconductorsubstrate bearing an insulation film with an aperture in the film ismaintained at a surface temperature for example of 260°-450° C. in thefilm forming chamber, and aluminum is selectively deposited on thesemiconductor exposed in the aperture by a thermal CVD method in a mixedatmosphere of alkylaluminum hydride gas such as DMAH and hydrogen gas.Naturally there may be deposited selectively a metal film principallycomposed of aluminum, such as Al--Si, by introduction of Si-containinggas, as explained before. Then, on the selectively deposited aluminumfilm and on the insulation film, a metal film composed solely orprincipally of aluminum is non-selectively deposited by sputtering.Subsequently, the non-selectively deposited metal film is patterned intoa desired shape to obtain the electrodes and wirings.

In the following the procedure will be explained in greater detail withreference to FIGS. 13 and 16A-16D. The substrate employed is, forexample, a monocrystalline silicon wafer with an insulation filmthereon, having apertures of different sizes therein.

FIG. 16A schematically illustrates a part of the substrate, whereinshown are a monocrystalline silicon substrate 401 constituting aconductive substrate; a thermal silicon oxide film 402 constituting aninsulation film; and apertures 403, 404 of different sizes.

The aluminum film formation, for forming an electrode in the firstwiring layer, is conducted in the following manner, with an apparatusshown in FIG. 13.

At first the above-mentioned substrate is placed in the loading chamber311, in which hydrogen is introduced to establish a hydrogen atmosphere,as explained before. The CVD reaction chamber 312 is evacuated by thevacuum system 316b to a pressure of ca. 1×10⁻⁸ Torr. However thealuminum film formation is possible at a pressure higher than 1×10⁻⁸Torr.

Then DMAH gas obtained by bubbling is supplied from the gas line 319,utilizing H₂ as carrier gas.

Also H₂ as the reaction gas is supplied from the second gas line 319',and the reaction chamber 312 is maintained at a predetermined pressure,by regulating the aperture of an unrepresented slow-leak valve. Atypical total pressure is about 1.5 Torr, with a DMAH partial pressureof ca. 5.0×10⁻³ Torr. Then, the halogen lamps 330 are turned on todirectly heat the wafer, and selective deposition of aluminum is thusconducted.

The DMAH supply is terminated after the lapse of a predetermineddeposition time. The deposition time is a time required by the aluminumfilm on Si (silicon substrate 1) to reach the thickness of SiO (thermaloxide film 2) and can be experimentally determined in advance.

The substrate surface temperature is maintained at about 270° C. bydirect heating. By the above-explained steps, an Al film 405 isselectively deposited in the apertures as shown in FIG. 16B.

The above-mentioned steps are called a first film forming step forelectrode formation in the contact hole.

Subsequently, the CVD reaction chamber 312 is evacuated by the vacuumsystem 316b to a pressure of 5×10⁻³ Torr or lower, and the Rf etchingchamber 313 is simultaneously evacuated to a pressure of 5×10⁻⁶ Torr orlower. After the chambers reach the above-mentioned pressures, thesubstrate is transferred from the CVD reaction chamber 312 to the Rfetching chamber 313 by the transfer means, by opening the gate valve310c, and the gate valve 310c is subsequently closed. The Rf etchingchamber 313 is evacuated by the vacuum system 316c to a pressure of 10⁻⁶Torr or lower, and is then maintained in an argon atmosphere of 10⁻¹-10⁻³ Torr by an argon supply from the argon supply line 322. Thesubstrate holder 320 for Rf etching is maintained at ca. 200° C., and anRF power of 100 W is supplied for about 60 seconds to the Rf etchingelectrode 321, thereby inducing an argon discharge in the Rf etchingchamber 313 and eliminating an unnecessary surface layer of the CVDdeposition film by etching with argon ions. The etch depth in this caseis about 100 Å calculated by oxide. The Rf etching of the surface of theCVD film in the RF etching chamber may however be dispensed with, sincethe surfacial layer of the CVD film, being transported in the vacuum, isfree from oxygen, etc., from the air. In such case, the Rf etchingchamber 313 serves for a rapid temperature change if there is a largetemperature difference between the CVD reaction chamber 312 and theSputtering chamber 314.

After the completion of Rf etching, the argon supply is terminated, andthe Rf etching chamber 313 is evacuated to 5×10⁻⁶ Torr. Then, after thesputtering chamber 314 is evacuated to 5×10⁻⁶ Torr or lower, the gatevalve 310d is opened, then the substrate is transferred from the Rfetching chamber 313 to the sputtering chamber 314 by the transfer means,and the gate valve 310d is closed.

Subsequently the sputtering chamber 314 is maintained in an argonatmosphere of 10⁻¹ -10⁻³ Torr as in the Rf etching chamber 313, and thesubstrate holder 323 is maintained at 200°-250° C. An argon discharge isinducted with a DC power of 5-10 KW to scrape the target of Al or Al--Si(Si: 0.5%) with argon ions, thereby depositing Al or Al--Sinon-selectively onto the substrate with a deposition speed of ca. 10000Å/min. This step is called a second film forming step for forming awiring to be connected with the electrode.

After the formation of a metal film of about 5000 Å on the substrate,the supply of argon and DC power is terminated. The unloading chamber isevacuated to 5×10⁻³ Torr or lower, the substrate is transferred theretoby opening the gate valve 310e. After the gate valve is closed, nitrogengas is introduced into the unloading chamber 311 to the atmosphericpressure, and the substrate is taken out by opening the gate valve 310f.

The above-explained second film forming step forms an Al film 406 on theSiO₂ film 402 as shown in FIG. 16C.

Wirings of a desired form can be obtained by patterning the Al film 406as shown in FIG. 16D.

[Experimental results]

In the following there will be given experimental results showing thesuperiority of the Al-CVD process and of the quality of the aluminumfilm deposited in the aperture.

There were employed plural substrates (sample 1-1) consisting ofmonocrystalline n-silicon wafers, bearing a thermally oxidized surfacialSiO₂ layer of a thickness of 8000 Å, in which apertures of differentsizes from 0.25×0.25 to 100×100 μm were patterned to expose theunderlying monocrystalline silicon therein.

These samples were subjected to aluminum film formation by the Al-CVDmethod, employing DMAH as the raw material gas and H₂ as the reactiongas with a total pressure of 1.5 Torr and a DMAH partial pressure of5.0×10⁻³ Torr, and with a regulated power to the halogen lamps to obtainthe substrate surface temperature within a range of 200°-490° C. bydirect heating. The obtained results are summarized in Table. 1.

                                      TABLE 1                                     __________________________________________________________________________    Substrate surface                                                             temp. (°C.)                                                                    200                                                                              230                                                                              250                                                                              260                                                                              270                                                                              280                                                                              300                                                                              350                                                                              400                                                                              440                                                                              450                                                                              460                                                                              470                                                                              480                                                                              490                         __________________________________________________________________________    Deposition                                                                            ← 1000-1500 →                                                              ← 3000-5000 →                                    speed (Å/min.)                                                            Throughput                                                                            ← 7-10 →                                                                      ← 15-30 →                                     (wafer/hr)                                                                    Si linear                                                                             ← not observed →                                          defects                                                                       Carbon content                                                                        ← not detected →                                          Resistivity                                                                           ← 2.7-3.3 →                                                                ← 2.8-3.4 →                                      (μΩcm)                                                               Reflectance (%)                                                                       ← 85-95 →                                                                     ← 90-95 →                                                                           ← ca. 60 →                  Hillock (>1 μm)                                                                    ← 1-10.sup.2 →                                                             ← 0-10 → ← 10-10.sup.4 →             density (cm.sup.-2)                                                           Spike formation                                                                       ← 0 →             ← 0-30 →                    (%) destruction                                                               frequency of                                                                  0.15 μm junction)                                                          __________________________________________________________________________

As will be apparent from Table 1, aluminum could be depositedselectively with a deposition speed as high as 3000-5000 Å/min. at asubstrate surface temperature of 260° C. or higher, obtained by directheating.

The aluminum film obtained in the aperture within a substrate surfacetemperature range of 260°-440° C. showed satisfactory characteristicswith no carbon content, a resistivity of 2.8-3.4 μΩcm, a reflectance of90-95%, a density of hillocks at least equal to 1.0 μm within a range of0-10, and almost no spike formation (represented by frequency ofdestruction of junctions of 0.15 μm).

On the other hand, within a substrate surface temperature range of200°-250° C., the film quality is considerably superior to that in theprior technology though it is somewhat inferior to that in thetemperature range of 260°-440° C., but the deposition speed could notexceed 1000-1500 Å/min. and the throughput was in a relatively low rangeof 7-10 wafers/hr.

Also at a substrate surface temperature equal to or higher than 450° C.,the quality of the aluminum film in the aperture deteriorated, with areflectance of 60% or lower, a density of hillocks of at least. 1 mwithin a range of 10-10⁴ cm⁻² and a frequency of alloy spike formationof 0-30%.

In the following there will be explained how the above-explained methodcan be favorably applied to an aperture such as a contact hole or athrough-hole.

The above-explained method can be favorably applied to a contact hole orthrough-hole structure of the following materials.

The following samples were subjected to aluminum film formation underthe same conditions as those employed for the sample 1-1.

A sample 1-2 was prepared by forming, on monocrystalline siliconconstituting a first substrate surface material, a silicon oxide film ofa thickness of 8000 Å by CVD as a second substrate surface material, andpatterning the silicon oxide film by a photolithographic process to formapertures of different sizes from 0.25×0.25 to 100×100 μm, therebylocalling exposing the monocrystalline silicon surface therein (thesample being hereinafter represented as "VD SiO₂ " (or simply SiO₂ (orsimply SiO₂)/monocrystalline silicon).

Also there were prepared:

a sample 1-3 of a boron-doped oxide film obtained by normal pressure CVD(hereinafter BSG)/monocrystalline silicon;

a sample 1-4 of a phosphor-doped oxide film obtained by normal pressureCVD (hereinafter PSG)/monocrystalline silicon;

a sample 1-5 of phosphor- and boron-doped oxide film obtained by normalpressure CVD (hereinafter BSPG)/monocrystalline silicon;

a sample 1-6 of a nitride film obtained by plasma CVD (hereinafterP-SiN)/monocrystalline silicon;

a sample 1-7 of a thermal nitride film (T-SiN)/ monocrystalline silicon;

a sample 1-8 of a nitride film obtained by low pressure CVD(LP-SiN)/monocrystalline silicone;

a sample 1-9 of a nitride film obtained by ECR (ECR-SiN/monocrystallinesilicon.

Furthermore there were prepared samples 1-11 to 1-179(sample numbers1-10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160and 170 are lacking) by taking all the combinations of following firstsubstrate surface materials of 18 kinds and second substrate surfacematerials of 9 kinds. The first substrate surface materials employedwere monocrystalline silicon (mono-Si), polycrystalline silicon(poly-Si), amorphous silicon (a-Si), tungsten (W), molybdenum (Mo),tantalum (Ta), tungsten silicide (WSi), titanium silicide (TiSi),aluminum (Al), aluminum-silicon (Al--Si), titanium-aluminum (Al--Ti),titanium nitride (Ti--N), copper (Cu), aluminum-silicon-copper(Al--Si--Cu), aluminum-palladium (Al--Pd), titanium (Ti), molybedenumsilicide (Mo--Si), and tantalum silicide (Ta--Si). Also the secondsubstrate surface materials employed were T-SiO₂, SiO₂, BSG, PSG, BPSG,P-SiN, T-Sin, LP-SiN, and ECR-SiN. In all these samples, there could beobtained aluminum films comparable in quality to that on theaforementioned sample 1-1.

Then an aluminum film Was non-selectively deposited by sputtering on thesubstrates subjected to selective aluminum deposition as explained aboveand was patterned.

The aluminum film obtained by the sputtering and the selectivelydeposited aluminum film in the aperture showed satisfactory contact withhigh electrical and mechanical durability, because of the excellentsurface state of the latter aluminum film in the aperture.

We claim:
 1. A method of producing an alignment mark which methodcomprises the steps of:providing a semiconductor substrate having at itssurface an insulating layer with a contact hole and a further apertureformed therein; depositing a conductive material selectively to fill thecontact hole and at least partially to fill the further aperture; anddepositing wiring material on said insulating layer, on said conductivematerial filling the contact hole, and on conductive material at leastpartially filling the further aperture, so that an alignment mark isproduced over the at least partially filled further aperture, whereinsaid further aperture exposes an area of the substrate larger than thearea of the substrate exposed by said contact hole, and said depositingof conductive material step is performed by selective chemical vapordeposition using an alkylaluminium hydride and partially fills thefurther aperture.
 2. A method according to claim 1, wherein thealkylaluminium hydride is dimethylaluminum hydride.
 3. A methodaccording to claim 1, wherein at least one of a Si-, Ti-, orCu-containing gas is mixed with the alkylaluminium hydride and hydrogento deposit selectively Al--Si, Al--Ti, Al--Cu, Al--Si--Ti, or Al--Si--Cuas the selectively deposited conductive material.
 4. A method accordingto claim 2, wherein at least one of a Si-, Ti-, or Cu-containing gas ismixed with the alkylaluminium hydride and hydrogen to depositselectively Al--Si, Al--Ti, Al--Cu, Al--Si--Ti, or Al--Si--Cu as theselectively deposited conductive material.
 5. A method of producing awired semiconductor device using an alignment mark for wire patternalignment, comprising the steps of:providing a semiconductor substratehaving at its surface an insulating layer with a contact hole and afurther aperture formed therein; depositing a conductive materialselectively to fill the contact hole and at least partially to fill thefurther aperture; depositing wiring material on said insulating layer,on said conductive material filling the contact hole, and on saidconductive material at least partially filling the further aperture sothat an alignment mark is produced over the at least partially filledfurther aperture, wherein said further aperture exposes an area of thesubstrate larger than the area of the substrate exposed by said contacthole, and said depositing of conductive material step is performed byselective chemical vapor deposition using an alkylaluminium hydride andpartially fills the further aperture; and patterning the wiring materialusing the alignment mark for pattern alignment.
 6. A method according toclaim 5, wherein the alkylaluminium hydride is dimethylaluminum hydride.7. A method according to claim 5, wherein at least one of a Si-, Ti-, orCu-containing gas is mixed with the alkylaluminium hydride and hydrogento deposit selectively Al--Si, Al--Ti, Al--Cu, Al--Si--Ti, or Al--Si--Cuas the selectively deposited conductive material.
 8. A method accordingto claim 5, wherein automatic pattern alignment is performed using laserlight reflected from the alignment mark.